Method of treating depression and tri-substituted amines therefor

ABSTRACT

The invention concerns a method for treating depression or senile dementia using a compound which acts selectively as an agonist of gamma aminobutyric acid (GABA) at GABA autoreceptors with the proviso that the compound is not fengabine and progabide.

This application is a divisional application of application U.S. Ser.No. 07/849,902, filed Mar. 12, 1992, (now U.S. Pat. No. 5,321,047,issued Jun. 14, 1994), which in turn is a continuation of applicationU.S. Ser. No. 07/534,401, filed Jun. 7, 1990, (abandoned), which in turnis a continuation of U.S. Ser. No. 07/360,518 filed 02 Jun. 1989(abandoned).

This invention relates to use of a new pharmacological activity and tocertain amines possessing said pharmacological activity, to processesfor preparing them and to pharmaceutical compositions containing them.More particularly this invention relates to the treatment of depression.

In the UK the annual referral rate for depression is around 300-400 per10⁵ population of whom 10-15% require hospitalisation. At present themost effective and safe treatment for severe depression involveselectroconvulsive therapy (ECT) where the patient receives a series ofcontrolled electric shocks. However such treatment understandablyengenders an atavistic fear and apprehension in many patients. It alsohas undesirable side-effects, notably disturbance of memory.

ECT is also expensive and time-consuming to administer, requiring thepresence of specialist doctors such as psychiatrists and anaesthetists.As an alternative to ECT, drug therapy provides a more acceptabletreatment for the patient but at the present time such therapy has notdisplaced ECT as the optimal treatment in severe cases because it is notalways effective. There is therefore a need for new drugs for thetreatment of depression, especially drugs having new modes of actionmimicking ECT.

The mode of action of ECT remains unknown but in recent years much hasbeen learnt about the biological effects of electroconvulsive shock(ECS) in animals. In particular, repeated ECS, given in ways closelymimicking those used to administer ECT clinically, elicits in rodentschanges in monoamine functions. These include: increased 5-HT-mediatedbehaviour, increased dopaminergic behaviour and depressedbeta-adrenoceptor binding and sensitivity of the coupled adenylatecyclase. The last is also seen following chronic treatment with a numberof antidepressant drugs.

The effects of repeated ECS are presumably a response or adaptation tothe acute effects of the seizures. Among these acute effects are amarked change in the release, synthesis and level of gamma aminobutyricacid (GABA) in the brain.--see Green A. R. et al, British J. Pharmacol.,92, 5-11 and 13-18 (1987) and Bowdler et al, ibid, 76, 291-298 (1982).

GABA is one of the most widespread and abundant transmitters in themammalian central nervous system and plays a major role in the controlof brain excitability. It is similarly implicated in thebenzodiazepine-mediated relief of anxiety. Recently, evidence has cometo light which suggests that GABA transmission may also be involved inthe therapeutic effects of some antidepressant treatments. Inparticular, new compounds designed as GABA agonists (eg. fengabine andprogabide) have been shown in preliminary clinical trials to haveantidepressant activity (vide infra). Taken together, these findingssuggest that interventions directed specifically at GABA transmissionmay provide the basis of novel therapies for the treatment of affectivedisorders.

At present three GABA receptors have been identified in the centralnervous system. These are (1) a GABA_(A) -receptor known to be mainlypostsynaptic and mediating inhibition of neuronal firing--see forexample Stephenson, F. A. Biochem, J., 249 pp 21-32 (1988); (2) aGABA_(B) receptor located presynaptically and mediating the inhibitionof release of a number of neuro-transmitters, eg. noradrenaline andaspartic acid, but not GABA--see for example Bowery, N. G. et al,Nature, 283, 92-94 (1980); and (3) a GABA autoreceptor which modulatesthe release of GABA from neurones--see for example Mitchell, P. R., andMartin, I. L. Nature, 274 904-905 (1978); Arbilla, S. Kanal, J. L andLanger, S. Z. Eur.J.Pharmac., 57, 211-217 (1979) and Brennan M. J. W. etal, Molec. Pharmac., 19, 27-30 (1981).

The pharmacological importance of these receptors is currently a subjectof investigation with a major part of the work involving the search foranticonvulsant drugs with a mode of action involving GABA_(A) receptors.Two drugs acting on GABA receptors, progabide and fengabine, have alsobeen shown to possess antidepressant effects in preliminary clinicaltrials--see P. L. Morselli et al, L.E.R.S. Vol 4 (1986) pp 119-126 andB. Scatton et al, Journal of Pharm. and Exp. Therapeutics., 241, 251-257(1987). The latter workers showed that fengabine possessed a biochemicalmode of action different from that of conventional antidepressants butthat the mechanism whereby fengabine exerted its antidepressant actionswas not yet clear. It was thought to derive from a GABAergic action,most likely at GABA_(A) receptors.

In the case of progabide, Morselli et al also attributed theantidepressant effect to an increased GABAergic transmission.

We provide evidence herein that the antidepressant effect of progabideand fengabine is in fact due to their agonist action at the GABAautoreceptor.

The GABA autoreceptor is capable of regulating the release of GABA fromGABAergic neurons which means an agonist at the autoreceptor woulddecrease the GABA release hence decreasing GABA function ie. an actionopposite to that of GABA_(A) agonists.

As far as we are aware it has not been suggested even remotely that theGABA autoreceptor is linked to an antidepressant effect. Previously theautoreceptor was believed to have the same pharmacology as the GABA_(A)site--see Molec. Pharm, 19,27-30 (1981). We have now surprisingly foundthat the GABA autoreceptor has its own distinct pharmacology and thatthere are compounds having selective agonist activity at the GABAautoreceptor. These compounds have valuable medical uses.

Accordingly in one aspect this invention provides a compound for use intreating depression characterised in that the compound has selectiveagonist activity at GABA autoreceptors and a pharmaceutical compositioncomprising such a compound.

This invention also provides a method for treating depression in humanswhich comprises administering an effective amount of a compound whichpossesses selective agonist activity at GABA autoreceptors.

This invention also provides a pharmaceutical composition for treatingdepression which comprises a compound possessing selective GABAautoreceptor agonist activity and a pharmaceutical acceptable carrier.

There is evidence that compounds acting at the benzodiazepine receptoras inverse agonists decrease GABA function in the brain and thusincrease acetylcholine transmission. In addition, probably as aconsequence of these actions, they facilitate memory in animals and man(see Sarter. M. et al. Trends in Neuroscience, 11 13-17, 1988).Compounds acting selectively as GABA autoreceptor agonists would beexpected to have similar actions.

Accordingly, another aspect of this invention provides a compound havingselective agonist activity at GABA autoreceptors for use in thepreparation of a medicament for treating senile dementia and other formsof memory impairment. This invention also provides a method of treatingsenile dementia and other forms of memory impairment in mammals whichcomprises administering an effective amount of a compound whichpossesses selective agonist activity at GABA autoreceptors.

In this invention it is preferred that the compound having GABAautoreceptor agonist activity is selective in that it has little or noactivity at GABA_(A) receptors. This is because GABA_(A) agonistactivity would tend to counteract the effect of the autoreceptoragonist. GABA_(A) antagonist activity tends to cause convulsions. Forexample the selectivity for the GABA autoreceptor relative to theGABA_(A) receptor is preferably greater than 100, most preferablygreater than 1000.

We have found that one general class of compounds in which selectiveGABA autoreceptor agonist activity can be observed is tri-substitutedamines in which one of the substituents is a 3- or 4-alkanoic acid whichitself may be substituted and derivatives thereof, such as an amide orsubstituted amide. Within such a general class the observation of GABAautoreceptor activity depends on the nature of the substituents.

In a further aspect of this invention there are provided compoundshaving a tri-substituted amine structure with one substituent being a 3-or 4-carbon alkyl group carrying a carboxylic acid or amide functionpossessing selective GABA autoreceptor agonist activity. Moreparticularly this invention relates to mono- and di-(arylalkyl)aminederivatives and related compounds possessing pharmacological activity,and intermediates of closely related structure.

Certain di-(arylalkyl)amine derivatives are known in the literature. Thereaction of dibenzylamine with 3-chloropropyl cyanide to give3-dibenzylaminopropyl cyanide and subsequent hydrolysis of the cyanideto give 4-dibenzylaminobutyric acid hydrochloride is described by M EGittos and W Wilson in Journal of the Chemical Society, (1955)2371-2376. The latter compound is also described in Chemical Abstracts106, 78248 (1987) where it is used to prepare derivatives ofdaunorubicin. 4-Dibenzylaminobutyramide and 4-dibenzylaminopropylcyanide are disclosed in Chemical Abstracts 97, 163499m as intermediatesin the preparation of 4-aminobutyric acid amide hydrochloride. Various-dibenzylaminoalkyl cyanides and related compounds are disclosed in J.Med. Chem., 1975 18(3) 278-284 as starting materials for fibrinstabilizing factor inhibitors.

Accordingly this invention provides a compound for use as apharmaceutical having formula: ##STR1## or a salt thereof, wherein Erepresents lower alkyl or a group Ar¹ --A¹ --; Ar¹ are the same ordifferent aryl groups (including heteroaryl) which are optionallysubstituted, eg. by one or more substituents commonly used inpharmaceutical chemistry such as lower alkyl, lower alkoxy, halogen,haloloweralkyl, haloloweralkoxy, cyano, amino (including substitutedamino eg. mono- or di-loweralkyl amino) and nitro;

A and A¹ are the same or different alkylene groups having one or twocarbon atoms linking Ar or Ar¹ to N and optionally substituted by loweralkyl and/or optionally substituted aryl, B is an alkylene group of 3 or4 carbon atoms, which may be substituted by lower alkyl;

D¹ represents CONR¹ R² or COOH where R¹ and R² are independentlyhydrogen, lower alkyl or aralkyl of 7 to 12 carbon atoms.

The compounds of formula Ia can be prepared from intermediates offormula Ib ##STR2## wherein Ar, A, E and B are as defined above and Drepresents CN, COhal, CH₂ OH, CHO or an ester function COOR.

By the term "lower" is meant a group containing 1 to 6 carbon atoms.

Examples of Ar and Ar¹ are mono- or bi-cyclic aryl groups such ascarbocyclic aryl groups of 6 to 10 carbon atoms (eg. phenyl or naphthyl)and heteroaryl groups of 5 to 10 ring atoms in which the heteroatom isselected from oxygen, nitrogen and sulphur (eg. pyridine, furan,thiophene) or aromatic groups containing two or more such heteroatoms(eg. thiazolyl). Bicyclic heteroaryl groups are exemplified by quinolineand benzofuran.

Examples of A and A¹ are independently --(CH₂)_(m) -- optionallysubstituted by lower alkyl and/or aryl where m is 1 or 2. Preferably Aand A¹ are independently --CHR³ -- where R³ is hydrogen, lower alkyl,eg. methyl or ethyl, or optionally substituted aryl as defined for Ar,eg. phenyl. Examples of B are --CH₂ CH₂ CH₂ -- and --CH₂ CH₂ CH₂ CH₂ --which groups may be substituted by lower alkyl such as methyl, eg. Brepresents --CH(CH₃)CH₂ CH₂ -- or --CH₂ CH(CH₃)CH₂ --.

Examples of R¹ and/or R² are hydrogen, methyl, ethyl, propyl and benzyl.

Some compounds of formula Ib are known compounds. Accordingly in afurther aspect this invention provides a compound of formula I(including compounds of formula Ia). ##STR3## wherein E, Ar, Ar¹, A, A¹and B are as defined above and D is COOH or CONR¹ R² wherein R¹ and R²are as defined above or D is CN, COhal, CH₂ OH, CHO or COOR where COORrepresents an ester function (eg. R=optionally substituted alkyl, oralkyl or aryl) providing that (i) neither Ar--A or E is unsubstitutedbenzyl and (ii) when B is --(CH₂)₄ -- and D is CN then E is other thanmethyl, ethyl or p-chlorobenzyl.

Compounds of formula I wherein D is CN, COhal, CH₂ OH, CHO or COOR whereR is as defined above are useful as intermediates to compounds offormula I wherein D is COOH or CONR¹ R².

The compounds of formula Ia as defined above possess pharmacologicalactivity especially activity affecting the nervous system. In particularthe compounds of formula Ia are inhibitors of gamma aminobutyric acid(GABA) release from nerve terminals via action on the GABA autoreceptor.

A number of compounds have previously been shown to be agonists at theGABA autoreceptor, for example muscimol, isoguvacine and THIP (see MerckIndex 1983 No. 9214) but such compounds are non-selective in that theyare also active at other GABA receptors (ie. GABA_(A) and/or GABA_(B)).As far as we are aware no medical use has been attributed to theabove-mentioned compounds based on their GABA autoreceptor activity.

Compounds showing selective properties at the GABA autoreceptor aredesirable since additional activity at the other GABA receptors wouldcause many side effects such as sedation and adverse muscle toneactions.

The compounds of formula Ia demonstrate activity at GABA autoreceptors,more specifically they demonstrate agonist activity as shown by standardin vitro test procedures. Advantageously compounds of formula Ia appearto be selective in that they display little or no activity at GABA_(A)or GABA_(B) receptors. The following test procedures were used tomeasure activity at (a) GABA autoreceptors and GABA_(B) receptors byinhibition of potassium-evoked GABA and noradrenalin release from ratcortex in vitro (Procedure 1); and (b) GABA_(A) receptors by enhancementof [3H]-flunitrazepam binding in rat cortex in vitro (Procedure 2):

PROCEDURE (1)

Slices (0.25×0.25×2.0 mm) of rat cerebral cortex are prepared using aMcIlwain tissue chopper. The slices are incubated in Krebs-Henseleitsolution containing [³ H]-GABA (10⁻⁷ M) and [¹⁴ C]-noradrenaline (10⁻⁷M) in the presence of amino-oxyacetic acid (AOAA) (10⁻⁵ M), pargyline(10⁻⁶ M) and ascorbic acid (10⁻⁴ M), for 20 minutes at 37° C., rinsedwith 5 ml aliquots of Krebs-Henseleit solution and transferred to 10superfusion chambers (volume 300 μl). The slices are continuouslysuperfused with Krebs-Henseleit solution (0.4 ml min⁻¹) containing AOAA(10⁻⁵ M) and fractions of the superfusate collected every 4 minutes.Transmitter release is induced by 4 minute exposure to a Krebs,Henseleitsolution containing 25 mM potassium (with concomitant reduction insodium to maintain osmolarity) after 68 (S₁) and 92 (S₂) minutes ofsuperfusion. The compound under study is added to the superfusing medium20 minutes prior to the second potassium stimulation. The residualradioactivity in the slices at the end of the experiment together withthat in the superfusate fractions is measured by liquid scintillationcounting using a dual label programme for tritium and carbon-14.

Calculations: The amount of radioactivity (either tritium or carbon-14)in each fraction is expressed as a percentage of the respective totalradioactivity in the tissue at the start of the respective collectionperiod. The amount of radioactivity released above basal by theincreased potassium is calculated and the ratio S2/S1 obtained. TheS2/S1 ratio from drug-treated slices is expressed as a percentage of thecontrol S2/S1 ratio. For compounds achieving inhibition of 30% or morepD₂ values are calculated from plots of inhibition of release versusconcentration of drug. Failure to inhibit the release of noradrenalineindicates that the molecule has no GABA_(B) agonist activity.

PROCEDURE (2)

Cortices from six or more rats are excised and homogenised in 50 volumes(volume/weight) 50 mM Tris buffer (pH 7.4 at 37° C.) using a Polytronhomogeniser on speed 5 for 30 seconds. Tissue is kept at 0° C.throughout the procedure. The homogenate is centrifuged at 40,000×g for15 minutes and the pellet resuspended (Polytron 5, 10 sec.) in 50volumes (original weight) of Tris buffer. Centrifugation andresuspension is repeated followed by incubation at 37° C. for 10minutes. The homogenate is centrifuged (40,000×g, 15 min), resuspendedin 10 volumes (original weight) Tris and stored below -20° C. for morethan 24 hours.

On the day of the experiment, membranes are thawed at 37° C. and made upto 20 volumes (original weight) with Tris Krebs (20 mM, see below). Themembranes are homogenised (Polytron 5, 30 sec), incubated at 37° C. for15 minutes and centrifuged at 20,000×g for 10 minutes. This wash andresuspension is repeated two more times with the final pelletresuspended in 100 volumes (original weight) Tris Krebs ready for use.

The test compound (50 μl) and 20 nM (final concentration) [³H]-flunitrazepam (50 μl) are dispensed in triplicate. The reaction isstarted by the addition of 900 μl of membrane preparation. After a 30minute incubation at 37° C. the reaction is stopped by filtrationthrough Whatman GF/B filters under reduced pressure using a BrandellCell Harvester, with two 7.5 ml filter washings. The radioactivityretained on the filters is measured by liquid scintillation counting.

Tris Krebs composition:

NaCl--136 mM, KCl--5 mM, MgSO₄ --2 mM, KH₂ PO₄ --2 mM, CaCl₂ --2 mM,Tris buffer (pH 7.4 at 37° C.)--20 mM, ascorbic acid--1 mM, disodiumethylenediamine tetraacetic acid--1 mM.

Calculations: Results are calculated as follows: ##EQU1##

RESULTS

In the aforementioned tests the following representative compounds gavethe results shown:

    ______________________________________                                                                Inhibition Enhance-                                                           of release ment of                                                GABA        of noradren-                                                                             [3H]-flu-                                              autoreceptor                                                                              aline at   nitrazepam                                 Compound    pD2 values  10.sup.-5 M                                                                              binding                                    ______________________________________                                        4-[N,N-Bis-(4-                                                                            7.0          0         0                                          Chlorobenzyl)-                                                                amino]butyric-acid                                                            4-[N,N-Bis-(4-                                                                            6.6          0         0                                          Chlorobenzyl)-                                                                amino]butyramide                                                              4-(N,N-Dibenzy-                                                                           7.0         >20%       0                                          lamino)butyra-                                                                mide                                                                          4-(N,N-Dibenzy-                                                                           7.1         20%        0                                          lamino)butyric acid                                                           4-[N,N-Bis-(4-                                                                            7.4         10%        0                                          Methylbenzyl)-                                                                amino]butyric                                                                 acid                                                                          4-[N,N-Bis-(3,4-                                                                          7.5          0         0                                          dichlorobenzyl-                                                               amino]butyric                                                                 acid                                                                          4-[N,N-Bis-(4-                                                                            6.0          0         0                                          methoxybenzyl)-                                                               amino]butyramide                                                              4-[N-(p-chloro-                                                                           7.5          0         0                                          benzyl)-N-methyl]                                                             aminobutyramide                                                               ______________________________________                                    

In the aforementioned tests fengabine was found to have a pD₂ value of8.0 at the GABA autoreceptor and little or no activity at GABA_(A) andGABA_(B) sites in vitro. We attribute the antidepressant activityobserved for fengabine to its potent selective GABA autoreceptoractivity. Progabide was also active at the GABA autoreceptor. We make noclaim to the use of fengabine or progabide in the preparation of amedicament for use as an antidepressant.

The compounds were also tested for their effect on a GABA synapse invivo in the following procedure:

PROCEDURE 3

Experiments were performed on male albino rats (240-280 g) lightlyanaesthetized with urethane (1.2-1.4 g/kg i.p.) or Halothane (0.7-1.0%in O₂). The animal's temperature was maintained between 36°-38° C. via athermostatically controlled heating blanket.

The caudate nucleus and substantia nigra were approached dorsally afterexposing the overlying cortex. Pulsations of the brain and cerebraloedema were minimised by allowing cerebral spinal fluid to leak from acisternal puncture. The exposed cortex was bathed in warm liquidparaffin throughout the experiment. A coaxial bipolar stimulatingelectrode (tip separation 0.25 mm) was positioned stereotaxically in thecaudate nucleus such that the tip of the electrode corresponded to thearea delineated by the co-ordinates L 2.5; A 8.5-95; D 5. (Paxinos andWatson, 1986). Square wave pulses (50-300 μA 0.1-0.2 msec duration) weredelivered at 0.5-1.0 Hz via the stimulating electrode to evokeinhibitory, GABA-mediated synaptic responses in nigral neurones.

Extracellular recordings were obtained from single neurones in theipsilateral substantia nigra via either the centre barrel (3.5M NaCl) ofa multibarrelled microelectrode or a single barrelled electrode (3.5MNaCl), attached to but protruding 10-20μ beyond, a multibarrelledelectrode. The electrodes were lowered into the substantia nigra via aremote controlled stepping micromanipulator such that the electrode tipcorresponded to the stereotaxic co-ordinates L1.5-2.5; A 3.0-4.0; D7.0-8.5 (Paxinos and Watson, 1986). Unit firing was amplified,continuously monitored on an oscilloscope, electronically counted anddisplayed by a chart recorder and fed into a computor for the generationof peristimulus time histogrames (PSTH) of synaptic responses. Eachouter barrel of the multibarrelled electrode was filled with aqueoussolutions of the following which were administered in the vicinity ofthe recorded neurones using standard microiontophoretic techniques:Compound of Example 5 (0.1M or 0.01M in 0.9% NaCl, pH 5.5), GABA (0.2M,pH 3.5), glycine (0.2M, pH3.5), dl-homocysteate (DLH) (0.2M, pH 7.2),N-methyl-D-Aspartate (NMDA) (0.05M in 0.165M NaCl, pH 7.0), quisqualate(0.02M in 0.165M NaCl, pH7.0), kainate (0.2M in 0.165M NaCl, pH 7.0) andbicuculline methochloride (BMC) (0.005M in 0.165M NaCl, pH 5.0). Effectsof agonist drugs on the GABA autoreceptor could be measured as anattenuation of the synaptic inhibition evoked by stimulation of thecaudate. GABA_(A) receptor agonism could be tested by ejecting drugdirectly onto the nigral meurone in the absence of synaptic inhibition.

The location of the recording and stimulating electrodes in the brainwere verified after each periment by histological examination.

Reference Paxinos G & Watson C (1986) The rat brain in stereotaxiccoordinates. Academic Press.

Result

In this test the compound of Example 5 almost abolishedsynaptically-evoked, GABA-mediated inhibition in the substantia nigrawithout affecting postsynaptic GABA_(A) receptors, when it was ejectediontophoretically in the vicinity of nigral neurones. This action of thecompound of Example 5 was reversible and is entirely consistent with aselective agonist action at the GABA autoreceptor

In another aspect this invention provides a compound of formula Ia foruse as a pharmaceutical.

This invention also provides processes for preparing the compounds ofthe invention, including processes for preparing the pharmacologicallyactive compounds of formula Ia via intermediates of formula I wherein Dis CN, COOR, CHO, CH₂ OH or COhal.

Compounds of formula I may be prepared by any one of the followingprocesses:

a) reacting a compound of formula II

    Ar--A--NH--E                                               (II)

wherein Ar, E and A are as defined above with a compound of formula III:

    hal--B--CN                                                 (III)

wherein B is as defined above and hal represents chlorine or bromine, togive a compound of formula I wherein D is CN,

or

b) carrying out a reductive alkylation of a compound of formula II asdefined above using a compound of formula IV

    OHC--B.sup.1 --CN                                          (IV)

wherein B¹ is an alkylene chain of 2 or 3 carbon atoms optionallysubstituted by lower alkyl, in the presence of a reducing agent such assodium cyanoborohydride to give a corresponding compound of formula Iwherein D is CN and B represents --CH₂ --B¹ --;

or

(c) reducing a compound of formula (V) ##STR4## wherein R⁴ is alkyl of 1to 5 carbon atoms or Ar¹ --A² --;

Ar, Ar¹, A and B are as defined above,

D³ represents CN, COOR or COOH and A² represents a direct bond oralkylene of 1 carbon atom optionally substituted by lower alkyl and/oraryl to give a corresponding compound of formula I wherein D is CN, COORor COOH and E is R⁴ CH₂ wherein R⁴ is as defined above;

or

(d) reducing a compound of formula (VI) ##STR5## wherein Ar, A and E areas defined above, B¹ is as defined in connection with formula IV and D²represents CN, COOR or CHO to give a corresponding compound of formula Iwherein B is --CH₂ B¹ -- and D is CN, COOR or CHO,

or

(e) partially hydrolysing a compound of formula I wherein D is CN togive a corresponding compound of formula I wherein D is CONH₂ ;

or

(f) hydrolysing a compound of formula I wherein D is CN or CONH₂ to givea corresponding compound of formula I wherein D is COOH;

or

(g) reacting a compound of formula I wherein D is COOR or COhal withammonia or an amine of formula HNR¹ R² to give a corresponding compoundof formula I wherein D is --CONR¹ R² ;

or

(h) hydrolysing an ester of formula I wherein D is COOR to give acarboxylic acid of formula I wherein D is COOH;

or

(i) oxidising an aldehyde of formula I wherein D is CHO to give an acidof formula I wherein D is COOH;

or

(j) oxidising an alcohol of formula I wherein D is --CH₂ OH to give analdehyde or an acid of formula I wherein D is CHO or COOH;

or

(k) oxidising a compound of formula ##STR6## wherein Ar, A, E and B areas defined above and D³ is COCH₃ --C≡CH or --CH═CH₂ to give a compoundof formula I wherein D is COOH;

or

(l) hydrolysing a compound of formula ##STR7## wherein Ar, A and E areas defined above, T¹ and T² are each independently an ester function, anitrile or an acyl group, and B¹ is an alkylene group of 2 or 3 carbonatoms optionally substituted by lower alkyl to give a correspondingcompound of formula I wherein B is --B¹ --CH₂ -- and D is COOH;

or

(m) esterifying an acid or acid halide of formula I wherein D is --COOHor COhal to give an ester of formula wherein D is --COOR;

or

(n) halogenating an acid of formula I to give an acid halide of formulaI wherein D is COhal;

or

(o) reducing an acid of formula I wherein D is COOH to give an alcoholof formula I wherein D is CH₂ OH,

or

(p) acidifying a compound of formula I to give an acid addition saltthereof or neutralising an acid addition salt to give the free baseform.

With regard to process (a) the reaction may be conveniently carried outin the presence of an inert solvent and a base such as a tertiary amine(eg. diisopropylethylamine) with heating if required. Examples ofsuitable inert solvents are dimethylformamide, acetonitrile anddimethylsulphoxide.

With regard to process (b) the reductive alkylation is convenientlycarried out in an inert solvent, depending on the reducing agent, andwithout heating. When the reducing agent is sodium cyanoborohydride thesolvent may be an aqueous alcohol such as aqueous ethanol. Catalytichydrogenation may also be used, eg using Pd/C and an alcohol solvent,eg. ethanol.

Process (c) and (d) may both be carried out using a suitable reducingagent not affecting the D¹ or D² group for example ionic hydrogenationsee Kursanor et al, Synthesis 1974, Vol 9, 633-651. Other reducingagents may be used, eg. diborane or Raney nickel.

With regard to process (e) the partial hydrolysis of the nitrile to givethe amide may be carried out in conventional manner under acidic orbasic conditions. Methods for carrying out the transformation areextensively described in the literature--see for example the textbookBuehler and Pearson, Survey of Organic Syntheses, Wiley Interscience,1970 pages 903-904, and references cited therein. The preferred methodis to carry out the hydrolysis using aqueous sodium hydroxide in thepresence of hydrogen peroxide and a phase transfer catalyst.

Process (f) may also be carried out in conventional manner using eitheracid or basic conditions as described in the literature. By way ofillustration reference is directed to the textbook Buehler and Pearson,ibid at pages 751-754.

Process (g) may also be carried out in conventional manner using ammoniaor amine preferably in alcoholic solution. Again by way of illustrationreference is drawn to the textbook Buehler and Pearson, ibid pps899-902. Where an acid halide is used as starting material it ispreferred to employ an acid salt thereof in order to minimise reactionof the starting material with itself.

The hydrolysis process (h) may be carried out under acidic or basicconditions in conventional manner eg. refluxing in 10% alkali metalhydroxide followed by acidification.

Processes (i) and (j) may be conveniently carried out using conventionalchemical oxidising agents, eg. potassium dichromate, potassiumpermanganate and oxygen/platinum catalyst. These and other methods aregiven in standard textbooks, see for example Buehler and Pearson, ibid,pps 545-549 and 760-764. Where process (j) is used to provide analdehyde, overoxidation to the acid can be avoided by selectiveoxidation methods as described on pages 546-8 of Buechler and Pearson.

With regard to process (k) oxidation of the compound of formula VIIwherein D³ is COCH₃ may be effected by treatment with halogen and alkali(ie. the well known haloform reaction) eg. by adding a solution ofsodium hypochlorite or hypobromite to the ketone in alcoholic solvent.Oxidation of the compound of the formula VII wherein D³ is CH═CH₂ or--C≡CH may be effected by using potassium permanganate, potassium iodateor ozone.

Hydrolysis process (l) is conveniently carried out under acidicconditions eg. refluxing in dilute sulphuric acid.

Esterification process (m) may be effected by conventional meansinvolving reaction with an alcohol ROH, see for example Buehler andPearson, ibid, pps 802-809. Conveniently the reaction of the acid may becarried out with the alcohol as solvent and in the presence of mineralacid (eg. HCl). The acid halide is conveniently in the form of an acidsalt prior to reaction with the alcohol and the reaction is preferablycarried out in base, eg. dimethylaniline or pyridine.

Process (n) may be carried out in the usual manner using a halogenatingagent, eg. phosphorus trichloride or tribromide, phosphorouspentachloride or thionyl chloride.

Reduction process (o) may be carried out using a reducing agent whichreduces acids to alcohols eg. a hydride such as borane.

The starting materials of formula II used in process (a) are knowncompounds or can be prepared by analogous methods eg. by reducing anamide of formula Ar--A--NHCO--E¹ where E¹ has one CH₂ group less than E.

Compounds of formula V can be prepared by acylating a correspondingcompound of formula Ar--A--NH--B--D¹ using an acid chloride of formulaR⁴ COCl. Compounds of formula Ar--A--NH--B--D³ can themselves beprepared by alkylating amines of formula NH₂ --B--D³ using a halide offormula Ar--A--hal.

Compounds of formula VI can be prepared by acylating amines of formulaAr--A--NH--E using an acid chloride of formula ClCO.B¹ --D² wherein thevariables have the values defined in connection with process (d).

Compounds of formula VII may be prepared by a process analogous toprocess (a) above using a compound of formula II and compound of formulahal--B--D³.

Compounds of formula VIII may be prepared by reacting a compound offormula IX: ##STR8## with a compound of formula T¹ CH₂ T², eg a malonicacid ester in the presence of a base, eg. sodium hydride or sodiumethoxide. The compound of formula IX may itself be prepared by reactionof phosphorus tribromide and a compound of formula I wherein D is --CH₂OH.

Starting materials for the processes described herein are knowncompounds or can be prepared by analogous methods for known compounds.

In any of the aforementioned reactions compounds of formula (and Ia) maybe isolated in free base form or as acid addition salts as desired.Examples of such salts include salts with pharmaceutically acceptableacids such as hydrochloric, hydrobromic, hyroiodic, sulphuric,phosphoric, nitric, acetic, citric, tartaric, fumaric, succinic,malonic, formic, maleic acid or organosulphonic acids such as methanesulphonic or tosylic acid.

When acidic substituents are present it is also possible to form saltswith bases eg. alkali metal (such as sodium) or ammonium salts eg.trimethylammonium. Such salts of the compounds of formula I and Ia areincluded within the scope of this invention.

This invention also provides pharmaceutical compositions comprising acompound of formula Ia or a pharmaceutically acceptable salt thereof anda pharmaceutically acceptable carrier.

For the pharmaceutical compositions any suitable carrier known in theart can be used. In such a composition, the carrier may be a solid,liquid or mixture of a solid and a liquid. Solid form compositionsinclude powders, tablets and capsules. A solid carrier can be one ormore substances which may also act as flavouring agents, lubricants,solubilisers, suspending agents, binders, or tablet disintegratingagents; it can also be encapsulating material. In powders the carrier isa finely divided solid which is in admixture with the finely dividedactive ingredient. In tablets the active ingredient is mixed with acarrier having the necessary binding properties in suitable proportionsand compacted in the shape and size desired. The powders and tabletspreferably contain from 5 to 99, preferably 10-80% of the activeingredient. Suitable solid carriers are magnesium stearate, talc, sugar,lactose, pectin, dextrin, starch, gelatin, tragacanth, methyl cellulose,sodium carboxymethyl cellulose, a low melting wax and cocoa butter. Theterm "composition" is intended to include the formulation of an activeingredient with encapsulating material as carrier, to give a capsule inwhich the active ingredient (with or without other carrier) issurrounded by carriers, which is thus in association with it. Similarlycachets are included.

Sterile liquid form compositions include sterile solutions, suspensions,emulsions, syrups, and elixirs.

The active ingredient can be dissolved or suspended in apharmaceutically acceptable carrier, such a sterile water, sterileorganic solvent or a mixture of both. The active ingredients can oftenbe dissolved in a suitable organic solvent, for instance aqueouspropylene glycol containing from 10 to 75% of the glycol by weight isgenerally suitable. Other compositions can be made by dispersing thefinely-divided active ingredient in aqueous starch or sodiumcarboxymethyl cellulose solution, or in a suitable oil, for instancearachis oil. The composition may be administered orally, nasally,rectally or parenterally.

Preferably the pharmaceutical composition is in unit dosage form, thecomposition is sub-divided in unit doses containing appropriatequantities of the active ingredient; the unit dosage form can be apackaged composition, the package containing specific quantities ofcompositions, for example packeted powders or vials or ampoules. Theunit dosage form can be a capsule, cachet or tablet itself, or it can bethe appropriate number of any of these in packaged form. The quantity ofactive ingredient in a unit dose of composition may be varied oradjusted from 1 to 500 mg or more, eg. 25 mg to 250 mg, according to theparticular need and the activity of the active ingredient. The inventionalso includes the compounds in the absence of carrier where thecompounds are in unit dosage form. Based on the results from animalstudies the dosage range for the treatment of humans using a compound offormula I will be in the range from about 1 mg to 2 g per day dependingon the activity of the compound.

The following Examples illustrate the invention and methods forpreparing compounds of the invention.

EXAMPLE 1 4-[N,N-Bis-(4-Chlorobenzyl)amino]butyronitrile

Bis-(4-chlorobenzyl)amine hydrochloride [prepared by reducingN-(4-chlorobenzyl)-4-chlorobenzamide with lithium aluminium hydride intetrahydrofuran] was basified using sodium Carbonate in methylenedichloride solvent to give after rotary evaporation 3.16 g of the freebase as an oil. This was then mixed with 4-bromobutyronitrile (1.19 ml),diisopropylethylamine (2.1 ml) and 25 ml of dry dimethylformamide andthe mixture stirred at 80° C. under nitrogen for 24 hours. On coolingwater (100cm³) was added and then the mixture was extracted with 1×50 mland 2×25 ml of methylene dichloride. The combined extracts were washedwith water, dried (MgSO₄), filtered and evaporated to give an oil. Thiswas further purified by column chromatography (silica column eluted withtoluene) to give 2.83 g of the title product as an oil. 2.8 g of thetitle compound was dissolved in 10 ml hot ethanol, acidified with 0.76 g(1 equiv,) of oxalic acid, diluted with ether and cooled to give, afterfiltration, the 1:1-ethanedioate salt (1.78 g) as colourless crystals,mp 124°-6° (dec).

Analysis

C₁₈ H₁₈ Cl₂ N₂.C₂ H₂ O₄ requires C,56.8; H,4.8; N,6.6. Found: C, 57.0;H, 4.9; N,6.2%.

EXAMPLE 2 4-[N,N-Bis-(4-Chlorobenzyl)amino]butyric Acid

1.36 g of 4-[N,N-bis-(4-chlorobenzyl)amino]butyronitrile (as produced inExample 1), water (25 ml) and concentrated hydrochloric acid (10 ml)were stirred and heated to reflux for 51/2 hours under a nitrogenblanket. After cooling, an oil was obtained which crystallised onscratching. The crystals were filtered, washed with dilute hydrochloricacid, then with diethyl ether and recrystallised from isopropanol ether.Filtration and drying at 60°/1 mm Hg gave the title compound as thehydrochloride salt (0.32 g) m.p. 206°-208° C.(dec)

Analysis

C₁₈ H₁₉ NO₂. HCl requires C,55.6; H,5.2; N,3.6. Found: C,55.4; H,5.2;N,3.7%.

EXAMPLE 3 4-[N,N-Bis-(4-chlorobenzyl)amino]butyramide

A solution of 4-[N,N-Bis-(4-chlorobenzyl)amino]butyronitrile (2.0 g)prepared according to Example 1 in dichloromethane (10 ml) was cooled inice, then treated with the phase-transfer catalyst ^(n) Bu₄ NHSO₄ (0.5g), 20% aq NaOH (3.2 ml ) and 30% H₂ O₂ (4.0 ml ). The mixture wasstirred vigorously at 0° for about half an hour, then at roomtemperature for 23 hours. After dilution with dichloromethane the layerswere separated, and the organic phase washed with water and with dil.aq. NaHSO₃, then dried (MgSO₄) Filtration and evaporation gave a syrup(2.26 g) which was flash-chromatographed on neutral alumina eluted withneat toluene (to remove starting material (0.3 g )) and then with 10%EtOH-toluene to recover the product (1.62 g). Repeat chromatography onsilica eluted with 2-5% EtOH-toluene gave the title compound (1.55 g;73.6%) as a syrup which set solid on standing. The resulting crystalshad m.p. 66°-76°.

Analysis

C₁₈ H₂₀ N₂ OCl₂ requires: C, 61.6; H, 6.0; N, 8.0. Found: C, 61.5; H,5.8; N, 8.0%.

EXAMPLE 4 4-(N,N-Dibenzylamino)butyramide

a) By a method analogous to Example 1 dibenzylamine was reacted with4-bromobutyronitrile to give 4-(N,N-dibenzylamino)butyronitrile, mp.45°-46° C.

b) Hydrogen peroxide (30% w/v; 5.6 ml), tetra-n-butylammoniumhydrogensulphate (1.70 g) and 5N aqueous sodium hydroxide (4 ml) wereadded to a stirred solution of 4-(N,N-dibenzylamino)butyronitrile (2.64g) in dichloromethane (10 ml) with water cooling. The mixture wasstirred vigorously at room temperature for 17 hours and dichloromethane(100 ml) was added. The layers were separated and the organic phase waswashed with saturated aqueous sodium chloride (10 ml), dried (Na₂ SO₄)and concentrated in vacuo to give a viscous oil (4.12 g). The productwas chromatographed on silica with eluant 20% ethylacetate/toluene→ethyl acetate and recrystallised from cyclohexane togive the title compound (1.86 g, 66%), m.p. 76°-77° C.

Analysis

C₁₈ H₂₂ N₂ O requires: C, 76.55; H. 7.85, N, 9.9. Found: C, 76.45; H,7.95; N, 9.8%

EXAMPLE 5 4-(N,N-Dibenzylamino)butyric Acid

A solution of 4-(N,N-dibenzylamino)butyronitrile (2.64 g) inconcentrated hydrochloric acid (50 ml) was refluxed for 3 hours. Thesolution was concentrated in vacuo to give a solid, which wasrecrystallised from acetic acid and water to give the title compound asthe monohydrochloride monoacetic acid salt (1.84 g), m.p. 138°-139° C.

Analysis

C₁₈ H₂₁ NO₂.HCl. C₂ H₄ O₂ requires: C,63.25; H,6.9; N,3.7%. Found: C,63.6; H, 7.2; N, 3.9

EXAMPLE 6 4-[N,N-Bis (4-methylbenzyl)amino]butyronitrile

A solution of 4-bromobutyronitrile (14.80 g) in dry dimethylformamide(100 ml) was added dropwise over 15 minutes to a stirred solution ofbis-(4-methylbenzyl)amine (22.53 g) and N,N-diisopropylethylamine (35 ml26 g) in dry dimethylformamide (100 ml). The solution was heated (oilbath 115° C.) under nitrogen for 4 hours. The solution was poured onto amixture of water (400 ml) and saturated aqueous sodium chloride (400 ml)and the mixture was extracted with ether (2×200 ml). The extracts weredried (Na₂ SO₄) and concentrated in vacuo to give an orange oil (39.55g). The product was chromatographed on silica with eluant diisopropylether, and dried at 100° C. at 0.1 mmHg for 4 hours to give4-[N,N-bis(4-methylbenzyl)amino]butyronitrile (26 g, 89%), which wasused in Example 7 without further characterisation.

EXAMPLE 7 4-[N,N-Bis-(4-methylbenzyl)amino]butyramide

Hydrogen peroxide (30% w/v; 5.67 ml), tetra-n-butylammoniumhydrogensulphate (1.70 g) and 5N aqueous sodium hydroxide (4 ml) wereadded successively to a stirred solution of4-(N,N-bis-(4-methylbenzyl)amino]butyronitrile (2.93 g) indichloromethane (10 ml), with water cooling. The mixture was stirredvigorously at room temperature for 16 hours then dichloromethane (100ml) was added. The layers were separated and the organic phase waswashed with saturated aqueous sodium chloride (1×10 ml), dried (Na₂ SO₄)and concentrated in vacuo to give a viscous oil (4.61 g). The productwas chromatographed on silica with eluant 20% ethylacetate/toluene→ethyl acetate and triturated with cyclohexane to givethe title compound (1.77 g), m.p. 85°-86° C.

Analysis

(Found: C,77.25; H, 8.35; N, 9.25; C₂₀ H₂₆ N₂ O requires C, 77.4; H,8.45; N, 9.0%.

EXAMPLE 8 4-[N,N-Bis-(4-methylbenzyl)amino]butyric Acid

4-[N,N-Bis-(4-methylbenzyl)amino]butyronitrile (2.93 g) was suspended inconcentrated hydrochloric acid (50 ml) and the mixture was refluxed (oilbath 130° C.) for 4 hours. The solution was concentrated in vacuo togive a foam (4.17 g). The product was triturated with hot water andcrystallised in ether at -78° C. to give the title compound as thehydrochloride, three quarters hydrate (2.82 g), m.p. 148°-151° C.

Analysis

C₂₀ H₂₅ NO₂.HCl.0.75H₂ O requires: C, 66.45; H, 7.65; N,3.9. Found: C,66.2; H, 7.2; N, 3.95%.

EXAMPLE 9 4-[N,N-Bis-(3,4-Dichlorobenzyl)amino]butyronitrile

Using a procedure analogous to Example 6, Bis-(3,4-dichlorobenzyl)amine(2.71 g, 8.09 mM) was reacted with 4-bromobutyronitrile (0.81 ml) togive the title compound as an oil 1.97 g.

Ir (film) CN 2230cm⁻¹.

EXAMPLE 10 4-[N,N-Bis-(3,4-dichlorobenzyl)amino]butyric Acid

A mixture of 4-[N,N-bis-(3,4-dichlorobenzyl)amino]butyronitrile (1.95g), NaOH (2.0 g) and ethanol (25 ml) was stirred and heated to refluxfor 6 hours under a nitrogen blanket. After cooling, the solvent wasevaporated in vacuo to give a paste which was taken up in water (30 ml),acidified with conc. HCl, stirred well and cooled in ice. The oil whichhad precipitated crystallised slowly. The crystals were filtered off,washed well with water, and recrystallised from dimethylformamide,diluted with a large volume of ether. The precipitated oil againcrystallised slowly. The crystals were triturated with hot isopropanol,diluted with ether, collected by filtration and dried at 50°/1 mm togive the title compound as the hydrochloride salt. (1.20 g), m.p.227°-231° (decomp).

Analysis

C₁₈ H₁₇ NO₂ Cl₄. HCl requires: C, 47.2; H, 4.0; N, 3.1. Found: C, 47.2;H, 4.0; N, 3.2%.

EXAMPLE 11 4-[N,N-Bis-(4-methoxybenzyl)amino]butyronitrile

A solution of 4-bromobutyronitrile (14.80 g) in dry dimethylformamide(100 ml) was added dropwise over 15 minutes to a stirred solution ofbis-(4-methoxybenzyl)amine (25.73 g) and N,N-diisopropylethylamine (35ml, 26 g) in dry dimethylformamide (100 ml). The yellow solution washeated under nitrogen at 110° C. for 4 hours and was allowed to cool.The solution was poured onto a mixture of water (400 ml) and saturatedaqueous sodium chloride (400 ml) and then extracted with ether (2×200ml). The extracts were dried (Na₂ SO₄) and concentrated in vacuo to givean oil (35.93 g). The product was chromatographed on silica with eluantdiisopropyl ether, and was triturated with cyclohexane to give the titlecompound (26.00 g), m.p. 56°-58° C.

Analysis

C₂₀ H₂₄ N₂ O₂ requires: C, 74.05; H, 7.45; N, 8.65. Found: C, 73.85, H7.4; N, 8.85%.

EXAMPLE 12 4-[N,N-Bis-(4-Methoxybenzyl)amino]butyramide

Hydrogen peroxide (30% w/v; 5.67 ml ), tetra-n-butylammoniumhydrogensulphate (1.70 g) and 5N aqueous sodium hydroxide (4 ml) wereadded successively to a stirred solution of4-[N,N-bis-(4-methoxybenzyl)amino]butyronitrile (3.24 g) indichloromethane (10 ml), with water cooling. The mixture was stirredvigorously at room temperature for 18 hours and dichloromethane (100 ml)was added. The layers were separated and the organic phase was washedwith saturated aqueous sodium chloride (1×10 ml), dried (Na₂ SO₄) andconcentrated in vacuo to give an oil (4.71 g). The product waschromatographed on silica with eluant 20% ethyl acetate/toluene →ethylacetate, and crystallised from diisopropyl ether at room temperature togive the title compound (2.21 g), m.p. 53°-54° C.

Analysis:

C₂₀ H₂₆ N₂ O₃ requires: C, 70.15; H, 7.65; N, 8.2%. Found: C, 70.0; H,7.75; N, 8.15%.

EXAMPLE 13 5-(N,N-Dibenzylamino)pentanonitrile

A solution of 5-bromopentanonitrile (16.20 g) in dry dimethylformamide(100 ml) was added dropwise over 15 minutes to a stirred solution ofdibenzylamine (19.73 g) and N,N-diisopropylethylamine (35 ml, 26 g) indry dimethylformamide (100 ml). The solution was heated (oil bath 110°C.) for 4 hours and was allowed to cool. The solution was poured onto amixture of saturated aqueous sodium chloride (400 ml) and water (400 ml)and the mixture was extracted with ether (2×200 ml). The extracts weredried (Na₂ SO₄) and concentrated in vacuo to give a mobile oil (30.32g).

The oil was chromatographed on silica with eluant diethyl ether to givethe title compound (23.17 g) as an oil which was used without furtherpurification in Example 14.

EXAMPLE 14 5-(N,N-Dibenzylamino)pentanoic Acid

A solution of 5-(N,N-dibenzylamino)pentanonitrile (2.75 g) inconcentrated hydrochloric acid (50 ml) was refluxed (oil bath 140° C.)for 4 hours. The solution was allowed to cool, and the productcrystallised. The mixture was concentrated in vacuo to give a whitesolid which was recrystallised from water, filtering out insolublematerial, to give the title compound (2.96 g), m.p. 202°-205° C.

Analysis

C₁₉ H₂₃ NO₂.HCl requires: C, 68.35; H, 7.25; N, 4.2. Found: C, 68.15; H,7.35; N, 4.2%.

EXAMPLE 15 4-N,N-(Bis-[2-(4-chlorophenyl)ethyl]amino)butyronitrile

In a manner analogous to Example 6, 5.08 g ofbis-[2-(4-chlorophenyl)ethyl]amine was reacted with 1.73 ml4-bromobutyronitrile to give the title compound (5.83 g).

EXAMPLE 16 4-N,N-(Bis-[2-(4-chlorophenyl)ethyl]amino)butyric Acid

A solution of the 4-(bis-[2-(4-chlorophenyl)ethyl]amino)butyronitrile(5.8 g) and NaOH (5.7 g) in ethanol (75 ml) was stirred and heated toreflux for 6 hours and, after cooling, the solvent was evaporated andthe residue was taken up in water, acidified with conc. HCl and theturbid mixture maintained at 5° C. overnight, during which time an oilprecipitated and solidified. The solid was collected by filtration andwashed with water. It was then boiled for 1 hour with conc. HBr, cooled,kept at 5° until resolidification had occurred, and the solid wascollected by filtration. Recrystallisation was twice effected bydissolution of the solid in hot isopropanol containing a few drops ofwater, followed by dilution with ether, to give crystals of the titlecompound as the hydrobromide salt, (4.03 g), m.p. 150°-2° (dec.;"sweating" occurs above 147°).

Analysis:

C₂₀ H₂₃ NO₂ Cl₂.HBr requires: C,52.1; H,5.2; N,3.0. Found: C,52.2;H,5.4; N,3.25%

EXAMPLE 17 Ethyl 4-[N,N-bis-(4-chlorobenzyl)amino]butanoate

a) An ice-cooled, stirred suspension of4-[N,N-bis-(4-chlorobenzyl)amino]butyric acid, hydrochloride salt (2.05g) (prepared according to Example 2) in absolute ethanol (100 ml) wastreated with HCl gas for 1/2 hour. The solution was warmed to roomtemperature and allowed to stand overnight. The solvent was evaporatedin vacuo, and the oily residue taken up in aqueous NaHCO₃ and extractedwith dichloromethane (2×25 ml). The combined extracts were washed withwater and dried (MgSO₄). Filtration and evaporation gave an oil (1.86 g)which was freed from residual acid by passage through a silica column,eluted with ethyl acetate. Evaporation of the eluate gave an oil (1.32g) which was dissolved in ethanol (5 ml) and treated with oxalic acid(0.30 g; 1 equiv.). Evaporation of the solvent and treatment of theresidue with hot ethyl acetate caused crystallisation to occur. Thecrystals were collected by filtration and recrystallised fromethanol-ethyl acetate to give the title compound as the 1:1 ethanedioatesalt (0.53 g) as colourless crystals, m.p. 123.5°-125°.

Analysis

C₂₀ H₂₃ NO₂ Cl₂.C₂ H₂ O₄ requires: C,56.2; H,5.4; N,3.0. Found: C,56.3;H,5.5; N,2.7%

b) The product of step (a) is converted to4-[N,N-bis-(4-chlorobenzyl)amino]butyramide by treatment with ammmoniumhydroxide.

EXAMPLE 18 4-[N,N-Bis-(4-Chlorobenzyl)amino)butanol

A stirred suspension of 4-[N,N-bis-(4-chlorobenzyl)amino]butyric acid,hydrochloride (prepared according to Example 2) (13.44 g) in drytetrahydrofuran (250 ml) was stirred and heated to reflux asborane-methyl sulphide (10 molar; 17 ml; 5 equiv.) was added dropwise.The mixture was stirred and heated to reflux under a nitrogen blanketfor 17 hours. After cooling, the mixture was decomposed by the dropwiseaddition of 10% aq H₂ SO₄. The organic solvent was evaporated in vacuoand the aqueous residue was diluted with 10% aq H₂ SO₄ (120 ml) andheated to reflux for 3 hours.

The cooled solution was poured onto aqueous Na₂ CO₃ and brine andextracted with dichloromethane (2×100 ml). The combined extracts, whichshowed a tendency to emulsify in the presence of water, were washed withbrine and dried (MgSO₄). Filtration and evaporation gave a viscous syrup(11.38 g) which was purified by passage through silica gel, eluted withneat toluene and then with 2-5% ethanol/toluene to give an oil (9.40 g).

A solution of the oil (7.50 g) in hot ethanol (25 ml) was treated with2.58 g (1 equiv) of fumaric acid. The crystals which separated overnightwere triturated with boiling iso-propanol, cooled and refiltered, togive crystals of the title compound as the 11/2 fumaric acid salt (3.70g) mp. 141°-143° (dec).

Analysis

C₁₈ H₂₁ NOCl₂.11/2 C₄ H₄ O₄ requires: C,56.3; H,5.3; N,2.7. Found: C,56.0; H,5.4; N, 2.6%

EXAMPLE 19 (a) 4-[(N-(1,1-diphenyl)methyl-N-benzyl)amino]butyronitrile

A solution of 4-bromobutyronitrile (7.40 g) in dry dimethylformamide (50ml) was added dropwise over 5 minutes to a stirred solution ofN-benzyl-1,1-diphenylmethylamine (13.67 g)(prepared by reductiveamination of benzophenone and benzylamine using sodium cyanoborohydride)and N,N-diisopropylethylamine (18 ml, 13 g) in dry dimethylformamide (50ml). The solution was heated at 120° C. under nitrogen for 42 hours andwas poured onto a mixture of saturated aqueous sodium chloride (200 ml)and water (200 ml). The mixture was extracted with ether (2×100 ml) andthe extracts were dried (Na₂ SO₄) and concentrated in vacuo to give anoil (21.27 g). The product was chromatographed on silica with eluantdichloromethane. Fractions containing the desired material wereevaporated to dryness at reduced pressure and dried at 110° C. at 0.1mmHg for 4 hours to give4-[(N-(1,1-diphenyl)methyl-N-benzyl)amino]butyronitrile as an oil (14.61g).

(b) 4-[(N-(1,1-Diphenyl)methyl-N-benzyl)amino] butyric Acid

A solution of the product of step (a) (3.40 g) in absolute ethanol (100ml) was treated with sodium hydroxide pellets (20.0 g). The mixture wasrefluxed for 4 hours and was concentrated in vacuo to give a solid.Water (200 ml) and ice (200 ml) were added and the mixture was acidifiedwith concentrated hydrochloric acid (100 ml) at 0° C. The mixture wasconcentrated in vacuo and the residue was triturated with isopropanol.The mixture was filtered and the solution was reconcentrated to give afoam (4.51 g). The product was dissolved in hot water and the mixturewas filtered through kieselguhr. The filtrate was concentrated in vacuoto give a solid (2.21 g), which was triturated with ethyl acetate, togive the title compound as the hydrochloride three quarters hydrate(1.90 g.), m.p. 166°-173° C.

Analysis

C₂₄ H₂₅ NO₂.HCl.0.75H₂ O requires C, 70.4; H, 6.75; N, 3.4. Found:C,70.65; H, 6.8; N, 3.05%.

EXAMPLE 20 a) 4-[N,N-Bis-(3-bromobenzyl)amino]butyronitrile

A mixture of N,N-bis-(3-bromobenzyl)amine (13.47 g; 0.038 mol),4-bromobutyronitrile (3.77 ml; 0.038 mol), diisopropylethylamine (10 ml;0.057 mol), potassium iodide (1 g) and dimethylformamide (30 ml) wasstirred under a nitrogen blanket at 80°-90° for 22 hours. After cooling,the solvent was evaporated and the residue was taken up in aq. Na₂ CO₃and extracted with dichloromethane. The combined extracts were washedwith aq. Na₂ CO₃ and dried (MgSO₄). Filtration and evaporation gave anoil (18.49 g), which was chromatographed on silica eluted with 1% v/vethanol-toluene. Evaporation of fractions containing product gave thetitle compound (12.36 g; 77.2%) as an oil. A solution of the product(0.84 g; 2 mmol) in hot ethanol (5 ml) was treated with oxalic acid(0.18 g; 2 mmol). Crystallisation occurred overnight and the crystalswere collected by filtration and recrystallised from ethanol-ether togive the 1:1 ethanedioate salt (0.22 g), mp. 120°-122° C.

Analysis

C₁₈ H₁₈ Br₂ N₂.(COOH)₂ requires: C, 46.9; H, 3.9; N, 5.5. Found: C,47.1;H,4.1; N, 5.3%.

b) 4-[N,N-Bis-(3-bromobenzyl)amino]butyric Acid

A solution of 4-[N,N-bis-(3-bromobenzyl)amino]butyronitrile (12 g) andethanol (120 ml) was stirred and heated to reflux for 17.5 hours undernitrogen. After cooling, the solvent was evaporated in vacuo. Theresidue was taken up in water (120 ml) and strongly acidified with conc.HCl (36 ml). The mixture was cooled in ice, causing an oil toprecipitate. The oil crystallised after standing overnight and wasfiltered off and triturated with hot isopropanol. After cooling, thecrystals were collected by filtration and washed with ether to givecrystals of the title compound as the hydrochloride salt (10.87 g), mp.156°-159° C.

Analysis

C₁₈ H₁₉ Br₂ NO₂. HCl requires: C,45.3, H,4.2; N,2.9. Found: C,45.0;H,4.5; N, 2.5%

EXAMPLE 21 a) 4-[N,N-Bis-(3-chlorobenzyl)amino]butyronitrile

A mixture of bis-(3-chlorobenzyl)amine (8.0 g; 0.03 mol), potassiumiodide (5.0 g; 0.03 mol), diisopropylethylamine (7.0 ml; 0.04 mol),4-bromobutyronitrile (3.0 ml; 0.03 mol) and dimethylformamide (25 ml )was stirred and heated to an oil-bath temperature of 80° C. for 18hours, under a nitrogen blanket. After cooling, the solvent wasevaporated and the residue taken up in dilute aqueous Na₂ CO₃ andextracted with dichloromethane (3×50 ml). The combined extracts werewashed with water and dried (MgSO₄). Filtration and evaporation gave anoil (11.0 g) which was chromatographed on silica eluted with neattoluene and then with 2% v/v ethanol-toluene. The fractions containingproduct were collected and evaporated to give the title compound as anoil (8.59 g).

A portion (1.1 g) of the oil was converted to the 1:1 ethanedioate saltby addition of oxalic acid (one equivalent) in isopropanol. Afterevaporation of the solvent, the 1.1 ethanedioate salt of the titlecompound was obtained by crystallisation from ethyl acetate, m.p. 74°-9°C.

Analysis

C₁₈ H₁₈ Cl₂ N₂. (COOH)₂ requires: C,56.7; H,4.8; N,6.6. Found: C,56.3;H,4.6; N,6.7%

b) 4-[N,N-Bis-(3-chlorobenzyl)amino]butyric Acid

A solution of 4-[N,N-bis-(3-chlorobenzyl)amino]butyronitrile (8.59 g;0.026 mol), NaOH (10 g; 0.25 mol) and ethanol (125 ml) was stirred andheated to reflux for 18 hours. After cooling the solvent was evaporatedin vacuo and the solid residue taken up in water (75 ml). After furthercooling in ice, conc. HCl was added until the mixture was strongly acid(ca. 25 ml required). The initially precipitated oil hardened to asolid, which was collected by filtration and recrystallised fromdimethylformamide-ether and then from 10% v/v water-isopropanol followedby dilution with ether. After drying at 45° C./1 mm the hydrochloridehemihydrate salt of the title compound was obtained (5.60 g). m.p.170°-173° (dec.; softens above 166°).

Analysis

C₁₈ H₁₉ Cl₂ NO₂. HCl. 1/2H₂ O requires: C,54.4; H,5.3; N,3.5. Found C,54.4; H,5.2; N,3.5%.

EXAMPLE 22 4-[N,N-Bis-(2-thienylmethyl)amino]butyric Acid

a) In a manner analogous to Example 21a,4-[N,N-bis-(2-thienylmethyl)amino]butyronitrile was prepared byalkylation of bis-(2-thienylmethyl)amine using 4-bromobutyronitrile.

b) In a manner analogous to Example 24-[N,N-bis-(2-thienylmethyl)amino]butyronitrile (12 g) was hydrolysedusing concentrated hydrochloric acid (200 ml) to give the title compoundas an oily-solid residue. Isopropanol (150 ml) was added and the mixturecooled with stirring. Precipitated NH₄ Cl was removed by filtration andthe filtrate was concentrated and filtered to remove further inorganicmaterial. The filtrate was partitioned between aqueous NaOH and toluene.After standing overnight, the layers were separated, the aqueous phasewas acidified to pH1, concentrated in vacuo, diluted with isopropanol,filtered to remove precipitated NaCl, and evaporated to dryness to givea solid.

The solid was chromatographed on silica eluted with 2% v/vethanol-toluene, then with 10%- and 20%-v/v ethanol-toluene. Theproduct-bearing fractions were evaporated, dissolved in isopropanol,filtered to remove a little solid material, concentrated in vacuo anddiluted with ether. The initially-precipitated gum crystallised afterstanding for 72 hours. The solid was collected by filtration, purifiedby trituration with boiling isopropanol, cooled and refiltered to givecrystals of the title compound, as the hydrochloride salt mp 158°-160°.

Analysis:

C₁₄ H₁₇ NO₂ S₂ HCl requires C, 50.7; H, 5.5; N, 4.2% Found C,50.5;H,5.6; N,4.1%.

EXAMPLE 23 4-[(N-4-Methylphenylmethyl-N-phenylmethyl)amino]butyric Acid

a) In a manner analogous to Example 21a,4-[(N-4-methylphenylmethyl-N-phenylmethyl)amino]butyronitrile wasprepared by alkylation of N-(4-methylphenylmethyl)benzenemethanamine(4.22 g) using 4-bromobutyronitrile (2 ml). Yield 4.45 g.

b) In a manner analogous to Example 10 the nitrile from step (a) abovewas hydrolysed using NaOH in ethanol to give, after acidification withHBr, the title compound as the hydrobromide, quarterhydrate salt, mp119°-125° C.

Analysis

C₁₉ H₂₃ NO₂. HBr. 1/4H₂ O requires: C 59.6; H 6.5; N, 3.7. Found: C,59.5, H, 6.75; N, 3.5%.

EXAMPLE 24 4-[N,N-Dibenzyl]amino-N'N'-dimethylbutyramide

A sample of 4-[N-N-dibenzyl]aminobutyric acid (8.51 g, 0.03 moles)(prepared according to Example 5) was dissolved in dry acetonitrile (50ml) under nitrogen. 1,1'-Carbonyldiimidazole (4.85 g) was dissolved indry acetonitrile and added dropwise over 1 hour. The mixture was stirredunder nitrogen for 96 hours. An excess of dimethylamine (10 g. 0.22moles) was added, and the mixture stirred for a further two hours.Evaporation gave a residue which was separated on a silica column withethyl acetate as eluant. Ten 50 ml fractions were collected; the productappearing in fractions 5-8. Evaporation gave an oil which was dissolvedin ether. Acidification with ethereal HCl to pH1 gave a precipitatewhich was recrystallised from ethyl acetate/isopropanol to give crystalsof the title compound as the hydrochloride, quarterhydrate, mp. 166-171.

Analysis

C₂₀ H₂₆ N₂ O. HCl. 1/4H₂ O requires C 68.5; H,7.9; N,8.0. Found C, 68.7;H, 8.0; N, 8.0%

EXAMPLE 25 4-[N,N-Bis-(1-Naphthalenemethyl)amino]butyric Acid

a) 1-Naphthoyl chloride (5.0 g, 0.026 moles) in CH₂ Cl₂ (25 ml) wasadded dropwise to a stirred solution of ice cooled1-naphthalenemethylamine in CH₂ Cl₂ (25 ml). A white precipitate formedimmediately. The mixture was stirred at room temperature for 3 hoursthen filtered. The precipitate was washed with water and hot ethanol,then dried to give N-(1-naphthalenylmethyl 1-naphthaleneacetamide (5.18g, 0.017 moles). The amide (5.18 g) was dissolved in tetrahydrofuran (25ml) then added dropwise to LiAlH₄ (0.63 g 0.016 moles) intetrahydrofuran (25 ml). The mixture was heated at reflux for 24 hours,then worked up by dropwise addition of water (0.6 ml), 15% aq NaOH(0.6ml) and water (1.9 ml). Filtration, drying (MgSO₄) and evaporation gavean oil (22.5 g) which was crystallised from ice-cold ethanol to giveN,N-bis-(1-naphthalenemethyl)amine (2.54 g)

(b) The amine from step (a) (2.54 g) was dissolved in DMF (20 ml), then4-bromobutyronitrile (0.76 ml, 0.0076 moles) and diisopropylethylamine(4.07 ml 0.023 moles) in DMF (25 ml) added dropwise. Potassium iodide (1g) was added and the mixture heated at reflux for 24 hours. Evaporationgave a solid which was taken up into Na₂ CO₃ (50 ml), extracted into CH₂Cl₂ (3×25 ml) dried (MgSO₄) and evaporated to give a solid. Separationon a silica column with 10% v/v ethyl acetate in toluene as eluant,followed by evaporation, gave4-[N,N-bis(1-naphthalenemethyl)amino]butyronitrile (1.54 g).

(c) The nitrile from step (b) (1.54 g) was dissolved in isopropanol (25ml), then NaOH (1.0 g, 0.024 moles) was added and the mixture heated atreflux for 24 hours. Evaporation gave a residue which was taken up intowater and extracted with CH₂ Cl₂ (3×30 ml). Drying and evaporation gavea solid which was partially dissolved in ether, then precipitated withethereal HCl. Filtration, trituration with HCl followed by ice-coldwater gave the title compound as the hydrochloride hemihydrate, (1.62 g)m.p. 187°-191° C.

Analysis

C₂₆ H₂₅ NO₂. HCl. 1/2H₂ O requires: C,72.8; H,6.4; N,3.3. Found: C,72.7; H,6.6; N, 3.5%

EXAMPLE 26 4-[N-(p-Chlorobenzyl)-N-methylamino]butyramide

A solution of 4-[N-(p-chlorobenzyl)-N-methylamino]butyronitrile (0.95 g;4.27 mmol) in dichloromethane (5 ml) was cooled in ice as ^(n) Bu₄ NHSO₄(0.3 g) was added, followed quickly by 20% w/v aq NaOH (1.6 ml) and 30%hydrogen peroxide (2.0 ml). The mixture was stirred vigorously, brieflyat 0° C. and then at room temperature, for 2 hours. After dilution withmore dichloromethane, the layers were separated, the organic phase waswashed with water and dried (MgSO₄). Filtration and evaporation gave anoil (0.83 g) which was chromatographed on silica eluted with toluenecontaining an increasing proportion of isopropanol (to 50% v/v). Theproduct was obtained as an oil (0.52 g) which set solid on standing, togive the title compound (0.52 g) m.p. 62°-64°.

Analysis

C₁₂ H₁₇ ClN₂ O requires: C, 59.9; H, 7.1; N, 11.6. Found: C, 60.0; H,7.1; N, 11.9%.

EXAMPLE 27 4-[N-Methyl-N-(4-chlorobenzyl)amino]butyric Acid

A mixture of 4-[N-methyl-N-(4-chlorobenzyl)amino]butyronitrile (4.65 g;0.021 mol) and NaOH (5 g; 0.125 mol) in ethanol (50 ml) was stirred andheated to reflux under a nitrogen blanket for 21 hours. The solvent wasevaporated to give a paste, which was dissolved in water (50 ml) andstrongly acidified with conc. HCl (ca. 12 ml). The solvents were againevaporated, and the residual, semi-crystalline mass was boiled brieflywith isopropanol, filtered, and the inorganic precipitate washed wellwith isopropanol. The filtrate was evaporated to give a syrup (7.47 g)which was crystallised in several crops from isopropanol/ether. Thecombined crops were triturated with boiling isopropanol, cooled,filtered and dried at 50°/1 mm to give the title compound as thehydrochloride salt (4.22 g) m.p. 149°-152°.

Analysis

C₁₂ H₁₆ ClNO₂. HCl requires C, 51.8; H, 6.2; N 5.0. Found: C, 51.5; H,6.2; N, 5.0%

EXAMPLE 28

In a manner analogous to Examples 26 and 27, nitriles of formula X shownbelow were hydrolysed to the corresponding acids or partially hydrolysedto the amide as shown below: ##STR9## in which formulae Ar, R and Brepresent:

    ______________________________________                                        Ar             R            B                                                 ______________________________________                                        2-furanyl      2-furanyl                                                      (CH.sub.2).sub.3 -                                                            2-furanyl      hydrogen                                                       (CH.sub.2).sub.3 -                                                            3-pyridyl      3-pyridyl                                                      (CH.sub.2).sub.3 -                                                            3-quinolyl     3-quinolyl                                                     (CH.sub.2).sub.3 -                                                            2-thiazolyl    2-thiazolyl                                                    (CH.sub.2).sub.3 -                                                            ______________________________________                                    

We claim:
 1. A compound of formula Ia ##STR10## or a pharmaceuticallyacceptable salt thereof, wherein E is lower alkyl or Ar¹ --A¹ --;Ar andAr¹ are the same or different aryl groups selected from phenyl ornaphthyl and heterocyclic aryl groups selected from thienyl, furanyl,pryidyl, thiazolyl, quinolinyl and benzofuranyl, provided that one of Arand Ar¹ must be such heterocyclic aryl group and that, when E is loweralkyl, Ar must be such heterocyclic aryl group, Ar and Ar¹ being each,independently, optionally substituted by one or more substituentsselected from lower alkyl, lower alkoxy, halogen, haloloweralkyl,haloloweralkoxy, cyano, amino, lower alkylamino, d-loweralkylamino andnitro; A and A¹ are the same of different alkylene groups having one ortwo carbon atoms linking Ar or Ar¹ to N, each optionally substituted bylower alkyl, or by an unsubstituted Ar or Ar¹ group as defined above; Bis an alkylene group of 3 or 4 carbon atoms which may be substituted bylower alkyl; D¹ represents COOH or CONR¹ R², wherein R¹ and R² areindependently hydrogen lower alkyl or aralkyl of 7 to 12 carbonatoms,wherein lower in connection with alkyl refers to such groupshaving 1 to 6 carbon atoms.
 2. A compound according to claim 1 whereinAr and Ar¹ when present are selected from phenyl, naphthyl, pyridinyl,furanyl, thienyl, quinolinyl and benzofuranyl which groups may beoptionally substituted by a substituent selected from one or more of thefollowing lower alkyl, lower alkoxy, halogen, haloloweralkyl, haloloweralkoxy, nitro, cyano and optionally substituted amino.
 3. A compoundaccording to claim 1 wherein the mono- or bi-cyclic heterocyclic aryl Aror Ar¹ group is selected from optionally substituted pyridinyl, furanyl,thienyl, quinolinyl, and benzofuranyl.
 4. A compound according to claim1 wherein A and A¹ are independently selected from --CHR³, where R³ ishydrogen, lower alkyl or an optionally substituted Ar group.
 5. Acompound according to claim 1 wherein B is --(CH₂)₃ -- or --(CH₂)₄ -- orsuch a group substituted by methyl.
 6. A compound according to claim 1wherein R¹ and R² are independently selected from hydrogen, methyl,ethyl, propyl or benzyl.
 7. A compound according to claim 1 which is4-[N,N-bis-(2-thienyl-methyl)amino]butanoic acid or a pharmaceuticallyacceptable salt thereof.
 8. A pharmaceutical composition comprising acompound of formula Ia ##STR11## or a pharmaceutically acceptable saltthereof, wherein E is lower alkyl or Ar¹ --A¹ --;Ar and Ar¹ are the sameor different aryl groups selected from phenyl or naphthyl andheterocyclic aryl groups selected from thienyl, furanyl, pryidyl,thiazolyl, quinolinyl and benzofuranyl, provided that one of Ar and Ar¹must be such heterocyclic aryl group and that, when E is lower alkyl, Armust be such heterocyclic aryl group and that, when E is lower alkyl, Armust be such mono- or bi-cyclic heterocyclic aryl group, Ar and Ar¹being each, independently, optionally substituted by one or moresubstituents selected from lower alkyl, lower alkoxy, halogen,haloloweralkyl, haloloweralkoxy, cyano, amino, lower alkylamino,d-loweralkylamino and nitro; A and A¹ are the same of different alkylenegroups having one or two carbon atoms linking Ar or Ar¹ to N, eachoptionally substituted by lower alkyl, or by an unsubstituted Ar or Ar¹group as defined above; B is an alkylene group of 3 or 4 carbon atomswhich may be substituted by lower alkyl; and D¹ represents COOH or CONR¹R², wherein R¹ and R² are independently hydrogen lower alkyl or aralkylof 7 to 12 carbon atoms,wherein lower in connection with alkyl refers tosuch groups having 1 to 6 carbon atoms, and a pharmaceuticallyacceptable carrier.
 9. A method of treating depression or seniledementia in a mammal so afflicted which comprises administering aneffective amount of a compound which acts selectively as an agonist ofgamma aminobutyric acid (GABA) at GABA autoreceptors wherein saidselective GABA autoreceptor agonist compound has the formula Ia:##STR12## or a pharmaceutically acceptable salt thereof, wherein E islower alkyl or Ar¹ --A¹ --;Ar and Ar¹ are the same or different arylgroups selected from phenyl or naphthyl and heterocyclic aryl groupsselected from thienyl, furanyl, pryidyl, thiazolyl, quinolinyl andbenzofuranyl, Ar and Ar¹ being each, independently, optionallysubstituted by one or more substituents selected from lower alkyl, loweralkoxy, halogen, haloloweralkyl, haloloweralkoxy, cyano, amino, loweralkylamino, d-loweralkylamino and nitro; A and A¹ are the same ofdifferent alkylene groups having one or two carbon atoms linking Ar orAr¹ to N, each optionally substituted by lower alkyl, or by anunsubstituted Ar or Ar¹ group as defined above; B is an alkylene groupof 3 or 4 carbon atoms which may be substituted by lower alkyl; and D¹represents COOH or CONR¹ R², wherein R¹ and R² are independentlyhydrogen lower alkyl or aralkyl of 7 to 12 carbon atoms,wherein lower inconnection with alkyl refers to such groups having 1 to 6 carbon atoms.